(173aj) Inter-Electronic and Inter-Valley Transitions in MoS2-WS2 Heterostructures and Alloys

Van der Waals heterostructures allow the integration of functionalities from different nanomaterials to obtain advanced, superimposed properties. Here, vertical MoS₂-WS₂ heterostructure grains were grown using atmospheric pressure chemical vapor deposition, and their optoelectronic properties were investigated. The field effect transistors fabricated from the heterostructure grains exhibited high photoresponsivity, which was influenced by the gating potential, as well as the measurement temperature. During the gating potential sweep from -5 V to +55 V, the light to dark source drain current ratio (I_light/I_dark) increased from 3 to 16 and from 2 to 7 at 60 K and 120 K, respectively. Alloy of Mo_xW_1-xS₂ grains were also obtained, which displayed valley coherence when irradiated with linearly polarized light. The degree of valley coherence was approximately 49% at room temperature. Such phenomena can be leveraged to realize novel optoelectronics, computing, and memory applications.